Normal Blood Calcium Levels Decrease as We Get Older

The amount of calcium in the blood changes as we mature. The highest blood calcium levels are seen in teenagers and young adults. By age 35 or 40, the blood calcium should be "in the 9's" almost all of the time. Most labs do not show normal calcium ranges according to the patients age. This causes delays in the diagnosis of hyperparathyroidism.

If you are sitting in front of your computer and this is the very first page of parathyroid.com that you have come to, and you got here because your doctor told you that you had high blood calcium, then go to our High Blood Calcium page first. This is an important page, so come back!

The role of the parathyroid glands is to maintain blood calcium levels in a very small, normal range. HOWEVER, this small normal range is different for different ages. The green area on this graph shows how the normal range for blood calcium changes as we go through life. The bottom X axis is our age in years, and the vertical Y axis is the amount of calcium in the blood. Note how the blood calcium increases quite dramatically when we are teenagers and growing bone (and getting taller). At age 26 our bones are the strongest and most dense (have the most calcium in them), and from that point on, the hormone changes in our bodies causes the amount of calcium in our blood to decrease. By the time we are 35 we should have most of our calcium levels below 10.2 mg/dl. Once we are over 40, we should not have calcium levels above 10.0 or 10.1. Almost all people over 35 have calcium levels "in the 9's" almost all the time. However, almost all teenagers and young adults have calcium levels in the low 10's.

Here is the BIG PROBLEM...

Laboratories that measure your blood calcium do NOT correct for your age!

One of the most common mistakes we see while evaluating thousands of patients every year for hyperparathyroidism and high blood calcium, is that doctors are not aware that the lab is not giving a "normal range" according to that patient's age. Instead, the lab will often give a normal range for "all humans" and that normal range will go up to 10.5 or even 10.7 mg/dl. Well technically the lab is correct, this is the range for all humans, but if the patient is 55 years old, then the upper limit of normal on that patient's labs SHOULD BE 10.0 mg/dl. The lab is not giving a normal blood calcium range for YOU, it is giving a normal range for all humans of all ages.

We see patients over 40 years old several times every daywho have had blood calcium levels over 10.0 mg/dl for years, but their doctor thinks this is normal because the lab says it is normal to have calcium up to 10.6. This is not correct! Blood calcium levels of 10.2 to 10.5 in a person over 35 indicates they have a parathyroid tumor. These patients have been going to the doctor telling them that they feel bad, but the doctor is unaware of the diagnosis of hyperparathyroidism because their lab did not give normal ranges for blood calcium according to the patient's age. UGH! I'm pulling my hair out--there are so many people who are suffering from a parathyroid tumor because of the lab being lazy. This is why you should always get a copy of your own blood tests and look them over (because your doctor is probably not paying close attention!).

Hypercalcemia Calculator: Calculate the Upper Limit of Blood Calcium for your Age

Enter your age and our calculator will give the upper limit of normal calcium for you.

Your Age

The Upper Limit of Calcium for your age is [Enter Your Age Above] mg/dl in the USA, and [Enter Your Age Above] mmol/L in most other countries.
Calcium levels above this should be considered too high for your age.

The upper limit of calcium varies with age with teenagers having the highest levels and adults over 50 having the lowest. Unfortunately, most labs don't give the upper limit of normal according to your age, so we have made this calculator for you. Note that blood calcium is measured differently in different parts of the world. Just as we measure distance in feet and miles in the USA, while other countries use meters and kilometers; in the USA we measure calcium with the units mg/dl while most other countries use the units mmol/L. The units your lab uses will be printed right next to your results.

Blood calcium levels above the normal range will cause problems.

This next graph goes one step further and shows very clearly that patients with hyperparathyroidism have high blood calcium, which is shown in blue. Note that diagnosing a person with hyperparathyroidism who is 18 years old is very different from diagnosing a person who is 65 years old. A normal, healthy teenager will have blood calcium levels that are above 10.0, and most of the time these healthy normal teenagers have calcium levels between 10.0 and 10.7 mg/dl. A patient who is 60 years old, however, should have calcium levels "in the 9's". A calcium level of 10.5 is normal in a person who is 21 years old, but signals the presence of a parathyroid tumor in an adult over 40 years old.

Teenagers with hyperparathyroidism typically have blood calcium levels between 10.9 and 12.3--it isn't subtle. For us adults over 35-40 years old, however, "frequent or persistent calcium levels above 10.1" means we are almost guaranteed to have a parathyroid tumor. As you will read below, a calcium level of 10.5 in an adult over 60 years old is more dangerous than a calcium level of 11.5 in a 20 year old. One small teaching point here... the blue area starts around age 10 because hyperparathyroidism is so rare below age 10 that it essentially doesn't exist. Remember, people of any age above 10 can get a parathyroid tumor, but the peak incidence is between the ages of 50 and 80. See our page on age for more about this. Hey folks, do us a favor, print this page and these graphs and take them to your doctor. No more than 1 doctor in 1000 understands that the labs don't correct normal ranges of blood calcium according to the patient's age. Teach your doctor, because a lot of you know more than they do (and you know who you are!).
(Note: about 6% of people with hyperparathyroidism can have calcium levels in the green area, not "all" patients with hyperparathyroidism have high blood calcium).

Most adults with hyperparathyroidism have blood calcium levels only little elevated.

The third and final graph in this series shows that 75% of people with primary hyperparathyroidism (and thus have a parathyroid tumor in their neck) have blood calcium levels that are just modestly elevated. Other pages of this website have different graphs that show average blood calcium and PTH for our last 20,000 patients, but here we can easily show that most parathyroid tumors increase the calcium in your blood only modestly which is shown by the purple area. Thus, most adults with hyperparathyroidism have calcium levels "in the 10's". Remember, adults over 35 or 40 should have calcium levels "in the 9's".

Now you see the biggest challenge we face... most people with a parathyroid tumor have only slightly or modestly elevated calcium levels and the lab is not giving normal ranges specific to the patient's age. So every day we see 4 or 5 patients who have had a parathyroid tumor for 6-8 years that has not been appreciated because their blood calcium level was not recognized as being high.

The height of the blood calcium is a very poor indicator of the severity of hyperparathyroidism.

The last concept for this page is very important, and something most doctors don't understand. In most things in life, and most things in medicine for that matter, a higher number is more significant than a lower number. A cholesterol of 350 is "worse" than a cholesterol of 310, for instance. Blood calcium levels are the big exception to this rule. The person with the "worse" hyperparathyroidism is the one who has had high blood calcium the LONGEST, not the one with the HIGHEST calcium.

Thus any doctor that is "watching" or "monitoring" your slightly high calcium to see if it goes any higher doesn't understand much about hyperparathyroidism. First, how high it is doesn't matter! A "slightly" high calcium for a number of years will cause tremendous troubles (discussed in great detail elsewhere). Second, this doctor is hurting you, because "keeping an eye on the calcium level" means he/she is adding to the duration of the high calcium, and it is the duration (how long it has been high) that causes all the troubles. The rate of high blood pressure, breast cancer, prostate cancer, renal failure, osteoporosis, A-fib, blood clots, hair loss, kidney stones, bone pain, muscle spasms, memory loss, and heart attack are all related to the duration of calcium (in years) over 10.1 mg/dl. How high the calcium has become is a very poor indicator of the severity of primary hyperparathyroidism.

A blood calcium of 11.5 is NOT more dangerous than a blood calcium of 10.5. If your doctor is waiting for your calcium to go higher, then he/she is watching a tumor slowly destroy your body and make many of you miserable. This is not good medical care. Get the tumor out of your neck and stop watching it.

If you understand the simple concepts on this one page, you know more about hyperparathyroidism than 99% of all doctors. We have a great story about the duration of high calcium in a crabby old lady in our parathyroid blog written by Dr Doug Politz. You will enjoy it.

By the way, you do NOT need an endocrinologist if you have hyperparathyroidism. You need a surgeon. And no, your insurance company does NOT require you to see an endocrinologist before you see a surgeon... there are no insurances in the US that have that requirement--because they all know it is cheaper for you to get the tumor out than it is to monitor the calcium for 5 years before you get it out.

What to read next

If you have high calcium, then you should download the CalciumPro app. Let the computer tell you what is wrong. Then you can skip those dumb scans and tests your doctor wants to do!

If you want to read more about calcium levels in the blood, how to diagnose parathyroid disease, and look at a graph of normal and high calcium levels, then go to our page on Diagnosing Parathyroid Disease.

Parathyroid.com is an educational service of the Norman Parathyroid Center, the world's leading parathyroid treatment center performing over 3,800 parathyroid operations annually (average 75 per week).